Various parts to be attached to the fuel tank like a part related to a valve or a pump, a part to secure the strength of the fuel tank, a part to control a ruffle of fuel, and so on are equipped in the fuel tank for a car. Time and labor over an installation work should be considered when these built-in parts are attached to an inner surface of the fuel tank. In consideration for this, it is preferable that these parts are attached to the fuel tank during a production process for producing the fuel tank in comparison with a method for attaching them to the fuel tank after the fuel tank has been molded.
There is a method described in a patent document 1 as an example of a prior art for attaching a built-in part to the fuel tank by utilizing a production process for producing the fuel tank. A method for producing the fuel tank is described in this document. This document describes that the production method comprises a step of providing a core with a built-in part; a step of carrying in the core between dies on which a parison is previously pressed; a step of fixing the built-in part to the parison by using the core; a step of molding the fuel tank in a state that the dies are closed again after the core is taken out; and a step of taking out the fuel tank from the dies. Furthermore, a technology capable of moving the core between a first core stop position and a third core stop position via a second core stop position is described. The first core stop position is a position for providing the core with a built-in part. The second core stop position is positioned between the first core stop position and the dies, and is a position for pre-heating and/or inspecting the built-in part provided in the core. The third core stop position is a position for the dies to close.
It seems that the dies and the core are moved up to under an extrusion device for extruding a parison, and the dies and the core close with the parison held by the dies and the core, and then the dies and the core return back to the third core stop position to carry out the step of fixing the built-in part, according to this document.